In horology, securing means permitting rigid attachment of one part onto another, must be as compact as possible in order that the resulting assembly exhibit a space requirement reduced as much as possible. When the resulting assembly must be reliable and resist tearing away caused by strong stresses while the base part which forms the support is a plastic material or, more generally, of a material substantially softer than brass, most of the traditional securing methods cannot be used in a satisfactory manner.
The use of rivets is particularly suitable for the assembly of timepieces within the framework or high mass production.
Nevertheless, securing by metallic rivets is often impossible to practice when the base part, in particular the base plate which must receive such rivet, is of plastic material. Effectively, the pressure which must be exerted on the rivet in order to upset the head and to form the riveting is sufficient to deform the plastic material of the base plate in an unacceptable manner.
Another technique currently used for securing an element onto a base part of plastic material calls for studs which are integral with the material of the base part, in particular the base plate of plastic material and which project normally to the surface of the latter. Such studs are introduced into corresponding holes formed in the element which it is desired to secure to the base part. Once the element is thus placed in the desired position on the said base part, the free ends of the studs are plastically deformed, for example by means of an ultrasonic technique in order to upset them and form a plastic riveting. The rivets produced by this technique being thus of plastic material, the assemblies obtained once again do not offer sufficient rigidity for certain applications.
Finally, the use of screws besides its relatively high cost price presents the drawback of not always enabling the obtention of sufficiently compact assemblies. Effectively, the heads of the screws form projecting portions going beyond the assembly.
A purpose of the present invention is to overcome the drawbacks of the prior art which have just been described in furnishing securing means exhibiting a relatively small space requirement capable of being put into place in a part of plastic material and permitting production of extremely rigid assemblies.